U.S. patent number 5,037,864 [Application Number 07/378,532] was granted by the patent office on 1991-08-06 for semi-continuous process for the preparation of polyurethane-urea aqueous dispersions.
This patent grant is currently assigned to The Dow Chemical Company. Invention is credited to Joginder N. Anand, Sven H. Ruetman.
United States Patent |
5,037,864 |
Anand , et al. |
August 6, 1991 |
Semi-continuous process for the preparation of polyurethane-urea
aqueous dispersions
Abstract
A semi-continuous process for the preparation of polyurethane
ionomer or polyurethane-urea ionomer aqueous dispersions which
comprises: A. in a first reaction zone contacting (i) an excess of
an aliphatic or cycloaliphatic diisocyanate, or mixture of an
aliphatic or cycloaliphatic diisocyanate with an aromatic
diisocyanate; (ii) an organic polyol, and (iii) a difunctional
isocyanate-reactive component containing an ionic group or
potential ionic group, under conditions such that an isocyanate
terminated ionic prepolymer is formed; with the proviso that where
an aromatic diisocyanate is used the equivalents of aromatic
diisocyanate used are less that the equivalents of the organic
polyol and difunctional isocyanate-reactive component; B.
transferring the prepolymer to a second reaction zone; C. in the
first reaction zone or the second reaction zone contacting the
prepolymer with a neutralizing agent under conditions such that the
ionic groups are neutralized; D. adding water to the second
reaction zone until a prepolymer in water emulsion with a particle
size of from about 300 .ANG. to about 10,000 .ANG. is formed; E.
adding to the second reaction zone a hydrocarbon polyamine
extender, a solution of a hydrocarbon extender, or a catalyst which
facilitates the chain extension of the prepolymer by water under
conditions such that a polyurethane or polyurethane-urea ionomer is
formed; and F. removing the polyurethane or polyurethane-urea
ionomer polyurethane-urea ionomer from the second reaction
zone.
Inventors: |
Anand; Joginder N. (Clayton,
CA), Ruetman; Sven H. (Walnut Creek, CA) |
Assignee: |
The Dow Chemical Company
(Midland, MI)
|
Family
ID: |
23493489 |
Appl.
No.: |
07/378,532 |
Filed: |
July 11, 1989 |
Current U.S.
Class: |
523/348; 524/840;
524/839 |
Current CPC
Class: |
C08G
18/0804 (20130101); C08G 18/12 (20130101); C08G
18/12 (20130101); C08G 18/302 (20130101); C08G
18/12 (20130101); C08G 18/3225 (20130101) |
Current International
Class: |
C08G
18/00 (20060101); C08G 18/12 (20060101); C08G
18/08 (20060101); C08G 018/12 () |
Field of
Search: |
;524/839,840
;523/348 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Welsh; Maurice J.
Assistant Examiner: Johnson; Rachel F.
Claims
What is claimed is:
1. A semi-continuous process for the preparation of polyurethane
ionomer or polyurethane-urea ionomer aqueous dispersions which
comprises:
A. in a first reaction zone contacting (i) a diisocyanate, (ii) an
organic polyol, and (iii) a difunctional isocyanate-reactive
component containing an ionic group or potential ionic group, under
conditions such that an isocyanate terminated ionic prepolymer is
formed;
B. transferring the prepolymer to a second reaction zone:
C. in the first reaction zone or the second reaction zone
contacting the prepolymer with a neutralizing agent under
conditions such that the ionic groups are neutralized;
D. adding water to the second reaction zone until a prepolymer in
water emulsion with a particle size of from about 300.ANG. to about
10,000.ANG. is formed:
E. adding to the second reaction zone a hydrocarbon polyamine
extender, a solution of a hydrocarbon extender, or a catalyst which
facilitates the chain extension of the prepolymer by water, under
conditions such that a polyurethane or polyurethane-urea ionomer is
formed: and
F. removing the polyurethane or polyurethane-urea ionomer from the
second reaction zone.
2. The process of claim 1 wherein the diisocyanate is aliphatic or
cycloaliphatic.
3. The process of claim 2 wherein the prepolymer is contacted with
a neutralizing agent in the first reaction zone.
4. The process of claim 3 wherein the prepolymer is chain extended
with a hydrocarbon polyamine extender under conditions such that a
polyurethane-urea ionomer aqueous dispersion is formed.
5. The process of claim 4 wherein the (i) excess of an aliphatic or
cycloaliphatic diisocyanate, (ii) organic polyol, and (iii)
difunctional isocyanate-reactive component containing an ionic
group or potential ionic group are contacted for between about 20
and about 150 minutes.
6. The process of claim 5 wherein the (i) excess of an aliphatic or
cycloaliphatic diisocyanate, (ii) organic polyol, and (iii)
difunctional isocyanate-reactive component containing an ionic
group or potential ionic group are contacted in the presence of a
polyurethane catalyst.
7. The process of claim 6 wherein the temperature (i) excess of an
aliphatic or cycloaliphatic diisocyanate, (ii) organic polyol, and
(iii) difunctional isocyanate-reactive component containing an
ionic group or potential ionic group are contacted at between about
20.degree. and about 100.degree. C.
8. The process of claim 7 wherein water is added to the prepolymer
in the second reaction zone at a temperature of between about
20.degree. and about 100.degree. C.
9. A semi-continuous process for the preparation of polyurethane
ionomer or polyurethane-urea ionomer aqueous dispersions which
comprises:
A. in two or more reaction zones adapted for preparing an
isocyanate terminated ionic prepolymer contacting (i) an excess of
a diisocyanate, (ii) an organic polyol, and (iii) a difunctional
isocyanate-reactive component containing an ionic group or
potential ionic group under conditions such that an isocyanate
terminated ionic prepolymer is formed:
B. sequentially transferring the neutralized prepolymer from the
two or more reaction zones adapted for preparing an isocyanate
terminated ionic prepolymer to a reaction zone adapted for
preparing a polyurethane polyurethane-urea ionomer aqueous
dispersion under conditions that the latter reaction zone
continuously forms polyurethane-urea ionomer aqueous
dispersions;
C. in the two or more reaction zones adapted for preparing an
isocyanate terminated ionic prepolymer contacting the prepolymer
with a neutralizing agent under conditions such that the ionic
groups are neutralized:
D. adding water to the reaction zone adapted for preparing a
polyurethane-urea ionomer aqueous dispersion until a prepolymer in
water emulsion with a particle size of from about 300.ANG. to about
10,000.ANG. is formed:
E. adding to the reaction zone adapted for preparing a
polyurethane-urea ionomer aqueous dispersion, a hydrocarbon
polyamine extender, a solution of a hydrocarbon extender, or a
catalyst which facilitates the chain extension of the prepolymer by
water, under conditions such that a polyurethane-urea or
polyurethane ionomer is formed; and
F. removing the polyurethane or polyurethane-urea ionomer from the
reaction zone adapted for preparing a polyurethane-urea ionomer
aqueous dispersion.
10. The process of claim 9 wherein the diisocyanate is aliphatic or
cycloaliphatic.
11. The process of claim 10 wherein the prepolymer is contacted
with a neutralizing agent in the two or more reaction zones adapted
for preparing an isocyanate terminated ionic prepolymer.
12. The process of claim 11 wherein the prepolymer is chain
extended with a hydrocarbon polyamine extender under conditions
such that a polyurethane urea ionomer aqueous dispersion is
formed.
13. The process of claim 12 wherein the (i) excess of an aliphatic
or cycloaliphatic diisocyanate, (ii) organic polyol, and (iii)
difunctional isocyanate-reactive component containing an ionic
group or potential ionic group are contacted for between about 20
and about 150 minutes.
14. The process of claim 13 wherein the (i) excess of an aliphatic
or cycloaliphatic diisocyanate, (ii) organic polyol, and (iii)
difunctional isocyanate-reactive component containing an ionic
group or potential ionic group are contacted in the presence of a
polyurethane catalyst.
15. The process of claim 14 wherein the (i) excess of an aliphatic
or cycloaliphatic diisocyanate, (ii) organic polyol, and (iii)
difunctional isocyanate-reactive component containing an ionic
group or potential ionic group are contacted at between about
20.degree. and about 90.degree. C.
16. The process of claim 10 wherein water is added to the
prepolymer in the second reaction zone at a temperature of between
about 20.degree. and about 100.degree. C.
17. A semi-continuous process for the preparation of a polyurethane
or polyurethane-urea ionomer aqueous dispersion which
comprises:
A. in one or more reaction zones adapted for preparing an
isocyanate terminated ionic prepolymer contacting (i) an excess of
a diisocyanate, (ii) an organic polyol, and (iii) a difunctional
isocyanate-reactive component containing an ionic group or
potential ionic group, under conditions such that an isocyanate
terminated ionic prepolymer is formed;
B. sequentially transferring the prepolymer from the reaction zones
adapted for preparing an isocyanate terminated ionic prepolymer to
a plug flow reaction zone adapted for preparing an aqueous
dispersion of the prepolymer under conditions such that prepolymer
is continuously fed to such reaction zone:
C. in the reaction zones adapted for preparing an isocyanate
terminated ionic prepolymer or in a zone of the plug flow reaction
zone contacting the prepolymer with a neutralizing agent under
conditions such that the ionic groups are neutralized:
D. adding water to the reaction zone adapted for preparing the
prepolymer aqueous dispersion until a prepolymer in water emulsion
with a particle size of from about 300.ANG. to about 10,000.ANG. is
formed;
E. flowing the prepolymer aqueous dispersion to a reaction zone
adapted for preparing a polyurethane or polyurethane-urea ionomer
aqueous dispersion:
F. adding a hydrocarbon polyamine extender, a solution of a
hydrocarbon extender, or a catalyst which facilitates the chain
extension of the prepolymer by water to the reaction zone adapted
for preparing a polyurethane or polyurethane-urea ionomer aqueous
dispersion under conditions such that a polyurethane-urea or
polyurethane ionomer aqueous dispersion is formed; and
G. removing the polyurethane or polyurethane-urea ionomer aqueous
dispersion from the reaction zone adapted for preparing the
polyurethane or polyurethane-urea ionomer aqueous dispersion.
18. The process of claim 17 wherein the diisocyanate is aliphatic
or cycloaliphatic.
19. The process of claim 18 wherein the prepolymer is contacted
with a neutralizing agent in the reaction zones adapted for
preparing an isocyanate terminated ionic prepolymer.
20. The process of claim 19 wherein the prepolymer is chain
extended with a hydrocarbon polyamine extender under conditions
such that a polyurethane-urea ionomer aqueous dispersion is
formed.
21. The process of claim 20 wherein the (i) excess of an aliphatic
or cycloaliphatic diisocyanate, (ii) organic polyol, and (iii)
difunctional isocyanate-reactive component containing an ionic
group or potential ionic group are contacted for between about 20
and about 150 minutes.
22. The process of claim 21 wherein the (i) excess of an aliphatic
or cycloaliphatic diisocyanate, (ii) organic polyol, and (iii)
difunctional isocyanate-reactive component containing an ionic
group or potential ionic group are contacted in the presence of a
polyurethane catalyst.
23. The process of claim 22 wherein the (i) excess of an aliphatic
or cycloaliphatic diisocyanate, (ii) organic polyol, and (iii)
difunctional isocyanate-reactive component containing an ionic
group or potential ionic group are contacted at between about
20.degree. and about 90.degree. C.
24. The process of claim 23 wherein water is added to the
prepolymer in the reaction zone adapted for preparing the
prepolymer aqueous dispersion at a temperature of between about
20.degree. and about 100.degree. C.
25. The process of claim 24 wherein hydrocarbon polyamine is added
to the prepolymer in the reaction zone adapted for preparing
polyurethane-urea ionomer aqueous dispersion at a temperature of
between about 20.degree. and about 100.degree. C.
26. The process of claim 25 wherein the residence time of the
prepolymer in the reaction zone adapted for preparing the
prepolymer aqueous dispersion is between about 30 seconds and about
30 minutes.
27. The process of claim 26 wherein the residence time of the
aqueous dispersion in the reaction zone adapted for preparing the
polyurethane-urea ionomer aqueous dispersion is between about 30
seconds and about 5 minutes.
Description
FIELD OF THE INVENTION
This invention relates to water borne ionic polyurethane-ureas and
polyurethanes and is more particularly concerned with an improved
process for the preparation of ionic polyurethane-ureas.
DESCRIPTION OF THE PRIOR ART
Stable aqueous dispersions of polyurethane-ureas and polyurethanes
containing chemically incorporated anionic or cationic groups have
long been known to be useful in various coating applications. The
coatings and sizings prepared from the dispersions have excellent
chemical resistance, abrasion resistance, toughness, and the
like.
D. Dieterich et al., as early as 1970, published one of the first
technical reviews on ionic polyurethane-urea aqueous dispersions:
see Angewante Chemie Intn'l., 9, pp. 40-50 (1970). This was
followed by a comprehensive review by the same author in Progress
In Organic Coatings, 9, pp. 218-340 (1981). For the most part, the
polymers are prepared from components which are essentially
difunctional in both isocyanate and isocyanate-reactive
ingredients. This means the polymers are essentially linear and
organic solvent soluble in their final form. However, cross-linked
polyurethane-urea aqueous dispersions are known as noted below.
Witt, U.S. Pat. No. 3,870,684, discloses aqueous dispersions of
polyurethane-ureas wherein the cross-linking is effected by mixing
as a solution in an organic solvent an isocyanate terminated
prepolymer having ionic groups with an aqueous solution of an
aliphatic polyamine containing a total of at least three primary
and/or secondary amine groups of which at least two are primary. A
preferred method of forming the dispersion involves diluting the
polyurethane mass, which carries salt-type groups and is dissolved
in a polar solvent, with about 70 to about 150 percent of its
weight of water, containing polyamine and then largely or
completely distilling off the organic solvent. Alternatively, the
organic polyurethane solution may be added to a given quantity of
water while stirring vigorously and the organic solvent may be
removed at the same time or afterwards. It is also possible to
inject the still liquid polyurethane mass free of solvent into
water, e.g., by means of nozzles, with or without the use of
compressed air, particles of the size of dispersion particles being
then formed immediately. However, the method of preparation
requires organic solvents and the need for highly functional
polyamines.
Hangauer, U.S. Pat. No. 4,203,883, discloses cross-linked
polyurethane-ureas closely related to those set forth in U.S. Pat.
No. 3,870,684 cited supra. The cross-linking is effected by
reacting an isocyanate terminated polyurethane prepolymer
containing tertiary amine neutralized carboxylic acid groups with a
triamine or mixture of triamine with diamine. Again, the employment
of organic solvent is favored at least in the preparation of the
prepolymer component. It is disclosed that chain extension is
frequently conducted in an aqueous medium such that the dispersion
of the urea-urethane polymer in water is directly formed. The
polyamine is preferably gradually added to the reaction medium
which contains the urethane prepolymer in order to prevent the
occurrence of localized high concentrations of the added reactant
which may lead to forming urea-urethanes having an unduly broad
molecular weight range. In the examples, the simultaneous slow
addition of polyamine and water is disclosed.
Nachtkamp, U.S. Pat. No. 4,172,191, discloses the preparation of
polyisocyanate addition products containing carboxylate and amide
groups, which may also contain urethane groups, by the reaction of
organic polyisocyanates with polyesters which contain carboxylate
groups, free carboxyl groups, and hydroxyl groups, to produce a
prepolymer, followed by chain lengthening. The formation of the
prepolymer may be carried out in the presence of organic solvents.
Neutralization is most easily carried out by adding tertiary amines
to the reaction mixture. The chain lengthening is carried out by
water or by a mixture of water and a polyamine or hydrazine. The
prepolymer may be dispersed in water before adding the chain
lengthening agent. This step may be carried out in the presence of
solvents used for the preparation of the prepolymer.
Generally speaking, the prior art teaches a preference for the use
of organic solvents throughout the preparation of the aqueous
dispersions. The prior art shows the preparation of aqueous
dispersions of polyurethane-ureas using primarily batch processing.
Such batch processing presents problems in commercial processing,
in particular each step is not separately controlled in the optimum
manner.
What is needed is a process for the continuous production of
aqueous dispersions of polyurethane-ureas which allows control of
each step separately without the use of solvent.
SUMMARY OF THE INVENTION
The present invention is a semi-continuous process for the
preparation of polyurethane ionomer or polyurethane-urea ionomer
aqueous dispersions which comprises:
A. in a first reaction zone contacting (i) an excess of: (ii) an
organic polyol, and (iii) a difunctional isocyanate-reactive
component containing an ionic group or potential ionic group under
conditions such that an isocyanate terminated ionic prepolymer is
formed:
B. transferring the prepolymer to a second reaction zone:
C. in the first reaction zone or the second reaction zone
contacting the prepolymer with a neutralizing agent under
conditions such that the ionic groups are neutralized;
D. adding water to the second reaction zone until a prepolymer in
water emulsion with a particle size of from about 300.ANG. to about
10,000.ANG. is formed;
E. adding to the second reaction zone; a hydrocarbon polyamine
extender, a solution of a polyamine hydrocarbon extender, or a
catalyst which facilitates the chain extension of the prepolymer by
water, under conditions such that a polyurethane or
polyurethane-urea ionomer is formed; and
F. removing the polyurethane or polyurethane-urea ionomer from the
second reaction zone.
This process allows the continuous production of polyurethane-urea
ionomer or polyurethane ionomer aqueous dispersions without organic
solvent with more accurate control of each step.
The ionic aqueous dispersions of this invention, by virtue of their
good film-forming properties are useful in a wide variety of
coating applications. The fact that the coatings are transparent
and have good tensile properties broadens the applications in which
they can be employed. Typically, they can be used as sizing in the
manufacture of high grade paper, coatings and impregnants for
textiles, leather, fibers, and the like. However, the toughness and
clarity of the films make them particularly useful as protective
coatings for other plastic articles made from such materials as
polycarbonates, acrylics, and the like. Window glazing, security
glass and aircraft canopies are but a few of the uses to which the
present films can be applied.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 demonstrates an embodiment of the process described herein,
wherein a first batch reactor is used for prepolymer formation and
a second reactor is used for polyurethane-urea ionomer formation.
FIG. 2 illustrates an embodiment wherein three batch prepolymer
reactors sequentially feed prepolymer to a continuous reactor where
water dispersion and chain extension occur. FIG. 3 demonstrates the
embodiment wherein there is one prepolymer reactor, a prepolymer
holding tank and a second reactor for water dispersion and chain
extension. FIG. 4 illustrates the embodiment in which two
prepolymer batch reactors sequentially feed one reactor designed
for water dispersion and chain extension.
DEFINITIONS
The term "hydrocarbon" as used herein with respect to the polyamine
extender component means a hydrocarbon residue having from about 2
to about 20 carbon atoms remaining after the replacement of the
appropriate number of hydrogen atoms by primary or secondary amine
groups: inclusive of said hydrocarbon residue are aliphatic of
C.sub.2 to C.sub.10, cycloaliphatic of C.sub.5 to C.sub.18,
aromatic of C.sub.6 to C.sub.20, and the like.
The term "aliphatic diisocyanate" means an organic isocyanate
containing two aliphatically bound isocyanate groups wherein the
aliphatic divalent residue is an alkylene radical having from about
6 to about 12 carbon atoms, inclusive, such as hexamethylene,
heptamethylene, octamethylene, nonamethylene, decamethylene,
undecamethylene, dodecamethylene, and isomeric forms thereof.
Another example is tetramethylxylene di-isocyanate.
The term "cycloaliphatic diisocyanate" means an organic
diisocyanate containing two cycloaliphatically bound isocyanate
groups wherein the cycloaliphatic divalent residue contains one or
two cycloalkylene radicals each cycloalkylene having from about 5
to about 8 carbon atoms, inclusive, such as cyclopentylene-1,3,
4-methylcyclopentylene-1,3, cyclohexylene-1,3, cyclohexylene-1,4,
2-methylcyclohexylene-1,4, 2,5-dimethylcyclohexylene-1,4,
cycloheptylene-1,3, cycloheptylene-1,4, 6-methylcycloheptylene-1,4,
cyclooctylene-1,3, cyclooctylene-1,4, cyclooctylene-1,5, and the
like: 4,4'-methylenebis(cyclohexylene),
4,4'-isopropylidenebis(cyclohexylene), 4,4'-dicyclohexylene, and
the like.
The term "aromatic diisocyanate" means an organic isocyanate
containing one or two aromatically bound isocyanate groups wherein
the aromatic divalent residue is an arylene or alkoxylene moiety
having from about 6 to about 20 carbon atoms, inclusive, such as
phenylene, benzylene, napthylene and the like.
The term "difunctional isocyanate-reactive component" means any
organic compound carrying two separate groups each capable of
reacting with an isocyanate group because of active hydrogens
according to the Zerewitinoff test, such as --OH, --NH.sub.2, --SH,
--COOH, and the like.
The term "ionic group or potential ionic group" means a group
either already in an anionic or cationic form or else, by
neutralization with a reagent, readily converted to said anionic or
cationic form respectively. Illustrative of such potential anionic
groups (and neutralized form) are --COOH(--COO.sup..crclbar.),
--SO.sub.2 OH(--SO.sub.2 O.sup..crclbar.), and
.dbd.POOH(.dbd.POO.sup..crclbar.); illustrative of such potential
cationic groups (and neutralized form) are
.tbd.N(.tbd.N--.sup..sym.), .tbd.P(.tbd.P--.sup..sym.), and
.dbd.S(.dbd.S--.sup..sym.).
The term "dispersion" as used herein means a two-phase system
comprising the ionic polyurethane-urea as the dispersed phase in
the continuous aqueous phase. It is to be understood that the
dispersed phase can be a liquid or a solid. Accordingly, the
present products comprehend both emulsions and suspensions.
DETAILED DESCRIPTION OF THE INVENTION
The process for the preparation of aqueous dispersions of
polyurethane-urea ionomers or polyurethane ionomers involves
generally, first, the preparation of a prepolymer from (i) an
excess of diisocyanate,(ii) an organic polyol, and (iii) a
difunctional isocyanate-reactive component containing an ionic
group or potential ionic group. Secondly, the ionic groups of the
prepolymer are neutralized, if they have not been previously
neutralized. The difunctional isocyanate-reactive component
containing an ionic group or potential ionic group (iii) may be
neutralized prior to formation of the prepolymer. Alternatively,
the neutralization agent may be added to the reaction mixture
during the formation of the prepolymer. After formation of the
prepolymer, and neutralization if necessary, the prepolymer is
dispersed in water to form a prepolymer in water dispersion.
Thereafter, the prepolymer is chain extended with a hydrocarbon
amine or reacted with a catalyst which catalyzes the reaction of
water with the prepolymer such that a water induced chain extension
of the prepolymer will take place.
The prepolymer formation step is performed in a batch reactor. The
steps of dispersion formation and chain extension may be performed
in a batch or continuous reactor. The neutralization may occur in
either reactor or third reactor which may be batch or continuous.
The limiting step is the formation of the prepolymer, as the
dispersion of the prepolymer and the chain extension proceed quite
fast. This allows the performance of the latter two steps in a
continuous fashion.
In general one or more, preferably two or more, reaction zones
adapted for the formation of the prepolymer are used to form the
prepolymer. After formation of the prepolymer and neutralization
when the prepolymer is transferred to a reaction zone adapted for
the formation of the polyurethane-urea ionomer aqueous dispersion.
Where two or more reaction zones adapted for the formation of the
prepolymer are used, the prepolymer is transferred to the reaction
zone adapted for the formation of the polyurethane-urea ionomer or
polyurethane ionomer aqueous dispersion in a sequential manner. In
such embodiment, the prepolymer reactors are operated such that
they are charged sequentially such that the intermediate is ready
for transfer as the second reaction zone is available to accept
such intermediate.
In one embodiment, there is one reaction zone adapted for the
formation of the prepolymer and one reaction zone adapted for the
formation of the polyurethane-urea or polyurethane ionomer aqueous
dispersion which is a batch reactor. In this embodiment, the
prepolymer once formed is transferred to the second reactor,
wherein the water dispersion and chain extension are performed
sequentially and the product is removed before the next batch of
prepolymer is ready for transfer. Neutralization if necessary may
be performed in either reactor.
In another embodiment, one reaction zone adapted for the formation
of the prepolymer is used and one continuous reactor is used for
the dispersion and the chain extension. In this embodiment the
prepolymer once formed is transferred to a holding vessel from
which the prepolymer is fed continuously to the continuous reactor
for water dispersion and chain extension. Preferably, the
prepolymer is continuously passed into and through the continuous
reactor where there are two zones wherein the first zone is adapted
for addition of the water to the prepolymer to form the dispersion,
and the second zone is adapted for the chain extension of the
prepolymer to give the polyurethane-urea or polyurethane ionomer
aqueous dispersion. In the first reaction zone water is added with
mixing continuously as the prepolymer passes through the reactor.
In the second zone, the hydrocarbon polyamine is added neat, or in
an aqueous dispersion or solution, continuously to the prepolymer
as it passes through the second zone. Alternatively, on aqueous
solution of a polyurethane catalyst may be added in this second
zone to affect water induced chain extension of the prepolymer. The
flow of the prepolymer through the continuous reactor can be set to
match the transfer of prepolymer from the prepolymer reactor to the
holding vessel, such that all the prepolymer is passed to the
continuous reactor during the time that the next batch of
prepolymer is being prepared.
In another embodiment, two or more batch reactors adapted for the
formation of the prepolymer are used and a continuous reactor is
used for the preparation of the water dispersion and chain
extension. Preferably, the prepolymer is continuously passed into
and through the continuous reactor where there are two zones, the
first zone adapted for addition of the water to the prepolymer to
form the dispersion, and the second zone adapted for the chain
extension of the prepolymer to give the polyurethane-urea or
polyurethane ionomer aqueous dispersion. In the first reaction
zone, water is added with mixing continuously as the prepolymer
passes through the reactor. In the second zone, the hydrocarbon
polyamine is added neat, or in an aqueous dispersion or solution,
continuously to the prepolymer as it passes through the second
zone. Alternatively, a catalyst for water chain extension is added
in this zone. In this embodiment, the prepolymer is sequentially
transferred to the continuous reactor such that a continuous flow
of prepolymer is fed to the continuous reactor.
Preferably, the diisocyanate, organic polyol, and difunctional
isocyanate-reactive component containing an ionic group or
potential ionic group are contacted in the absence of a solvent.
This contacting occurs with mixing, such mixing is achieved by a
means which provides uniform mixture such means well known in the
art. In one preferred embodiment, such mixing may be achieved by a
slow stirring agitator in a Pfaulder type reactor, where
temperature can be controlled. Reaction times for the prepolymer
formation are affected by the batch size, reactor temperature,
mixing efficiency, and presence or absence of catalyst. Generally,
reaction times are long enough to allow completion of the
prepolymer formation. Preferred reaction times are between about 20
and about 150 minutes. The reactants are preferably contacted at
about ambient temperature. Thereafter, the reaction mixture may be
heated to a temperature of between 20 and about 100.degree. C.
If necessary, the prepolymer is neutralized by contacting it with a
compound which converts the ionic moieties to the salt form.
Preferably, tertiary amines are used. It may be preferable to cool
the prepolymer before neutralization. Such cooling is advisable
where a low boiling tertiary amine is used, or where there is a
risk of unwanted reaction due to the reactivity of the materials
present. Temperatures for neutralization are preferably between
20.degree. C. and about 100.degree. C.
The dispersion of the prepolymer in water involves the addition of
water to the prepolymer. Generally, the water is added until a
phase inversion occurs to give a prepolymer in water dispersion. It
is preferable that the dispersion take place at relatively low
temperatures to prevent the water from chain extending the
prepolymer. The time for dispersion is sufficient to allow
formation of a stable prepolymer in water dispersion with a
particle size of between about 300.ANG. to about 10,000.ANG., more
preferably between about 300.ANG. to about 3,000.ANG.. The time
depends upon the style of reactor and how efficient the mixing is.
In a batch reactor the time for dispersion is between about 30
seconds and about 60 minutes, more preferably between about 5
minutes and about 30 minutes. In a continuous process the residence
time prepolymer in the dispersion zone is between about 30 seconds
and about 10 minutes. Mixing is achieved by contacting the
reactants under shear designed to generate the desired particle
size. Such methods are known in art. In one preferred embodiment, a
high speed agitator designed for providing good shear to form and
control the desired particle size is used.
The chain extension is effected by contacting the prepolymer
dispersion with a hydrocarbon polyamine or a catalyst, which
catalyzes the reaction of water with the prepolymer such that water
chain extends the prepolymer. This contacting can take place in a
batch reactor by adding the hydrocarbon polyamine or catalyst, or a
solution or dispersion of the hydrocarbon polyamine or catalyst, to
the reactor after the dispersion of the prepolymer in the water. In
the embodiment, where the hydrocarbon polyamine is the chain
extender, the addition of the polyamine should occur shortly after
formation of the dispersion so as to reduce the risk of chain
extension by the water. The time required in a batch reactor is
controlled by the size of the reactor and the mixing of the
reactor. Generally, the time required is that time necessary for
the completion of the conversion of the prepolymer to a
polyurethane-urea or polyurethane. Preferably, the time is between
about 30 seconds and about 30 minutes, more preferably between
about 5 minutes and about 20 minutes. In a continuous process, the
prepolymer dispersion is flowed through a reaction zone where the
polyamine or catalyst is added to the dispersion under conditions
to form a polyurethane or polyurethane-urea ionomer. In a
continuous process, the residence time of prepolymer in the chain
extension zone is between about 30 seconds and about 10 minutes.
Mixing is achieved by means well known in the art. For example,
mixing may be affected by controlling the speed of the agitator to
maintain the emulsion and prevent coalescence of the particles.
The preparation of the aqueous dispersions of the ionic
polyurethane or polyurethane-ureas is carried out using any of the
conventional conditions and ingredients known to those skilled in
the art. Typical preparative methods are disclosed in the U.S. Pat.
Nos. 3,870,684; 4,108,814: 4,203,883: 4,408,008; and 4,501,852
whose disclosures relative thereto are incorporated herein by
reference.
The diisocyanates (i) which can be employed for the isocyanate
terminated prepolymer (A) preparation are defined above.
Illustrative but non-limiting of the diisocyanates are
1,6-hexamethylene diisocyanate, 1,7-heptamethylene diisocyanate,
1,8-octamethylene diisocyanate, 1,9-nonamethylene diisocyanate,
1,10-decamethylene diisocyanate, 1,11-undecamethylene diisocyanate,
1,12-dodecamethylene diisocyanate, 2,2,4-trimethylhexamethylene
diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate,
tetramethylene xylene diisocyanate, and the
(3-isocyanatopropoxy)-(3-isocyanatopropyl)arylenes such as
1-(3-isocyanatopropoxy)-4-(3-isocyanatopropyl)benzene described in
U.S. Pat. No. 4,051,166, 1,4-bis(2-isocyanatoethyl)cyclohexane, and
the like; isophorone diisocyanate otherwise identified as
1-isocyanato-3-isocyanatomethyl-3,5,5-trimethylcyclohexane; and
cycloaliphatic diisocyanates such as methylenebis(cyclohexyl
isocyanate) including the 4,4'-isomer, the 2,4'-isomer, and
mixtures thereof, and all the geometric isomers thereof including
trans/trans, cis/trans, cis/cis and mixtures thereof, cyclohexylene
diisocyanates (1,2-; 1,3-; or 1,4-), 1-methyl-2,5-cyclohexylene
diisocyanate, 1-methyl-2,4-cyclohexyl diisocyanate,
1-methyl-2,6-cyclohexylene diisocyanate,
4,4'-isopropylidenebis(cyclohexyl isocyanate),
4,4'-diisocyanatodicyclohexyl, 1,4-diisocyanatocycloheptylene,
1,4-diisocyanatocyclooctylene, and the like. Aromatic diisocyanates
which may be useful include the following, 1,5-naphthylene
diisocyanate, 4,4'-diphenylmethane diisocyanate,
4,4'-diphenyldimethylmethane-diisocyanate, di- and
tetralkyldiphenylmethane diisocyanate, 4,4'-dibenzyl diisocyanate,
1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, and
toluylene diisocyanate.
Preferred as a group are the cycloaliphatic diisocyanates and
preferred within this group are the methylenebis(cyclohexyl
isocyanates) with the 4,4'-isomer being particularly preferred.
Aromatic diisocyanates may be used alone or in admixture with
aliphatic or cycloaliphatic di-isocyanates. Preferably, where
aromatic diisocyanates, those with the isocyanate moieties on the
aromatic ring, are used, they are used in combination with
aliphatic or cycloaliphatic diisocyanates. In such embodiment, the
equivalents of aromatic diisocyanate are preferably less than the
equivalents of the organic polyol and the difunctional isocyanate
reactive compound which are reactive with isocyanate moieties. It
is believed that the prepolymers will under such circumstances have
terminal aliphatic or cycloaliphatic isocyanate moieties. The
aliphatic and cycloaliphatic isocyanate moieties are less reactive
than aromatic moieties and therefore greater control of the chain
extension can be had.
The organic polyols (ii) can be any of the high molecular weight
polyols exemplified in the incorporated references above.
Preferably, the molecular weight falls in the range of from about
500 to about 6,000, more preferably, from about 1,000 to about
3,000. The term "molecular weight" as used herein means the number
average molecular weight as determined by end-group analysis or
other colligative property measurement.
Exemplary of the diols which can be employed are: polyether diols,
polyester diols, hydroxy-terminated polycarbonates,
hydroxy-terminated polybutadienes, hydroxy-terminated
polybutadiene-acrylonitrile copolymers, hydroxy-terminated
copolymers of dialkyl siloxane and alkylene oxides such as ethylene
oxide, propylene oxide and the like, and mixtures in which any of
the above polyols are employed as major component (greater than 50%
w/w) with difunctional amine-terminated polyethers and
amino-terminated polybutadiene-acrylonitrile copolymers.
Illustrative of polyether diols are polyoxyethylene glycols,
polyoxypropylene glycols, polyoxybutylene glycols which,
optionally, have been capped with ethylene oxide residues, random
and block copolymers of ethylene oxide, propylene oxide, and
butylene oxide, random and block copolymers of tetrahydrofuran and
ethylene oxide and or propylene oxide, and products derived from
any of the above by reaction with difunctional carboxylic acids or
esters derived from said acids in which latter case ester
interchange occurs and the esterifying radicals are replaced by
polyether polyol radicals. The preferred polyether polyols are
random and block copolymers of ethylene and propylene oxide of
functionality approximately 2.0 and polytetramethylene glycol
polymers.
Illustrative of polyester diols are those prepared by polymerizing
s-caprolactone using an initiator such as ethylene glycol,
ethanolamine and the like, and those prepared by esterification of
polycarboxylic acids such as phthalic, terephthalic, succinic,
glutaric, adipic, azelaic and the like acids with dihydric alcohols
such as ethylene glycol, butanediol, cyclohexanedimethanol and the
like.
Illustrative of the amine-terminated polyethers are the aliphatic
primary diamines structurally derived from polyoxypropylene glycols
Polyether diamines of this type are available from Texaco under the
trademark JEFFAMINE.
Illustrative of polycarbonates containing hydroxyl groups are those
prepared by reaction of diols such as propane-1,3-diol,
butane-1,4-diol, hexan-1,6-diol, 1,9-nonanediol,
2-methyloctane-1,8-diol, diethylene glycol, triethylene glycol,
dipropylene glycol and the like with diarylcarbonates such as
diphenylcarbonate or with phosgene.
Illustrative of the silicon-containing polyethers are the
copolymers of alkylene oxides with dialkylsiloxanes such as
dimethylsiloxane and the like: see, for example, U.S. Pat. No.
4,057,595.
Illustrative of the dihydroxy-terminated polybutadiene copolymers
are the compounds available under the trade name Poly BD Liquid
Resins from Arco Chemical Company. Illustrative of the dihydroxy-
and diamine-terminated butadiene/acrylonitrile copolymers are the
materials available under the trade name HYCAR hydroxyl-terminated
(HT) Liquid Polymers and amine-terminated (AT) Liquid Polymers,
respectively.
The most preferred diols comprise the preferred random and block
polyether diols and polytetramethylene glycols set forth above
otherwise referred to as polyalkyleneoxy diols and with
polyethyleneoxy-capped polypropyleneoxy diols being most
specifically preferred.
In another embodiment, the polyol can be a triol. The triol can be
any of the organic polyols known in the urethane art to be
trihydric in functionality and which fall into the molecular weight
ranges set forth above. The triols can be identically obtained to
those diols described above except for the use of initiators and
starting materials leading to trihydroxy functionality. For
example, polyether triols are readily available or easily prepared
in the form of polyoxyethylene triols, polyoxypropylene triols,
polyoxybutylene triols, the latter two optionally capped with
ethyleneoxy residues, including random and block copolymers. All of
these polyether triols are generically identified as
polyalkyleneoxy triols and are prepared by the reaction of the
corresponding ethylene, propylene, butylene oxides with
trifunctional initiators such as glycerine, trimethylolpropane, and
the like; optionally, the triols can be prepared from
tetrahydrofuran and a trifunctional starter to yield the
corresponding polytetramethyleneoxy triols; polyester triols while
more difficult to synthesize with the overall trifunctionality than
the polyalkyleneoxy triols above, are nevertheless still useful as
triol components: typical trifunctional polyester triols are those
prepared from s-caprolactone with an initiator such as glycerine,
trimethylolpropane and the like; further illustrative examples of
triols include polycarbonate triols prepared by reaction of triols
such as trimethylolpropane or glycerine with diphenylcarbonate or
phosgene: and mixtures of any of the above triols as the major
component (greater than 50% w/w) with trifunctional
amine-terminated polyethers.
A preferred class of triols comprises the polyalkyleneoxy triols,
particularly those having a molecular weight of from about 500 to
about 3,000. Even more preferred are the polyethyleneoxy-capped
polypropyleneoxy triols having a molecular weight from about 500 to
about 2,000.
In one preferred embodiment, the component (ii) for preparing said
isocyanate terminated ionic prepolymer comprises a mixture of at
least one diol with at least one triol. The proportions in which
the triol is to be employed will vary somewhat according to its
molecular weight. Branching and eventual cross-linking of the final
polymer will be controlled largely by the molecular weight factor.
As molecular weight of the triol decreases, then branching in the
prepolymer leading to possible cross-linking therein, and, most
assuredly, in the final polyurethane or polyurethane-urea ionomer
will occur. Accordingly, the ultimate film properties desired will
dictate triol molecular weight and the proportions in which to use
it. Advantageously, the triol can be present in the mixture in up
to about 50 hydroxyl equivalent percent. That is to say, of the
total hydroxyl equivalents employed in the prepolymer preparation,
up to about 50 percent can be contributed by the triol component.
Above the 50 percent level will generally lead to visible gel
formations in the aqueous dispersions. Preferably, the polyol
mixture (ii) comprises from about 5 to about 50 equivalent percent
of said triol and from 95 to 50 percent of said diol. More
preferably, the triol falls in a range of from about 10 to about 40
percent with diol being 90 to 60 percent.
Known difunctional chain extenders such as the aliphatic C.sub.2 to
C.sub.10 glycols as typically exemplified by ethylene glycol,
1,4-butanediol, 1,6-hexanediol, and the like are not specifically
excluded from the present polymers. At the same time, their use is
not particularly necessary in the prepolymer (A) preparation unless
particularly high hardness is desired in the final films.
The difunctional isocyanate-reactive components (iii) are necessary
to provide for the water dispersibility of both the prepolymer and
final polyurethane or polyurethane-urea ionomer as discussed
typically in U.S. Pat. No. 3,479,310. Such components contain an
ionic group or potential ionic group as defined above and include
any of those compounds disclosed in U.S. Pat. No. 4,408,008,
particularly column 6, line 63 through column 7, line 57 whose
disclosure with respect to these compounds is incorporated herein
by reference. Additionally, the U.S. patent disclosures recited in
this referenced disclosure including 3,412,054; 3,419,533:
3,479,310; and 4,108,814 are also incorporated herein by reference
with respect to the difunctional isocyanate-reactive ionic or
potential ionic compounds disclosed.
As noted and defined above, the ionic definition includes both
anionic and cationic character. Additionally, the term "neutralize"
as used herein for converting potential ionic to ionic groups
refers not only to neutralization using true acids and bases but
also includes quaternarization and ternarization. The potential
anionic groups typically include carboxylic acid groups, sulfonic
acid groups, and phosphoric acid groups which when incorporated
into the difunctional isocyanate-reactive component (iii) can be
neutralized before, during, or after the prepolymer formation to
form the corresponding carboxylate anion, sulfonate anion, and
phosphate anion by treatment with such inorganic or organic bases
as sodium hydroxide, potassium hydroxide, potassium carbonate,
ammonia, tertiary amines such as triethylamine, tripropylamine,
tributylamine, and the like. In respect of the potential cationic
groups, these typically include tertiary amine, phosphine, and
sulfide groups which when incorporated into the difunctional
isocyanate-reactive component (iii) can be quaternated or ternated
as the case may be by neutralization or quaternarization of the
tertiary amine, or reacting the phosphine or sulfide with compounds
capable of alkylating the phosphine or sulfide groups. Sometimes it
is more convenient to have the precursor phosphine or sulfide
groups as a separate reagent with the actual quaternizing or
ternarizing moiety in the difunctional component (iii).
The isocyanate-reactive groups themselves as defined above are
those having active hydrogen atoms and include hydroxyl, amino,
thiol, and carboxylic acid. Preferred of the functional groups are
the dihydroxy and diamino compounds with dihydroxy functionality
most preferred.
Illustrative but non-limiting of the compounds containing a
potential anionic (ionic) group are tartaric acid (mono-, or
di-sodium salt), 2,6-dihydroxy benzoic acid (sodium salt, potassium
salt, triethylammonium salt), 2,8-dihydroxynaphthoic acid-3 (sodium
salt, potassium salt, triethylammonium salt), 3,4-diaminobenzoic
acid (sodium salt, potassium salt, triethylammonium salt),
1,7-dihydroxynaphthalenesulfonic acid-3 (sodium salt, potassium
salt, triethylammonium salt), 1,8-dihydroxynaphthalenedisulfonic
acid-2,4 (sodium salt, potassium salt, triethylammonium salt),
2,4-diaminotoluenesulfonic acid-5 (sodium salt, potassium salt,
triethylammonium salt), the sulfonate diols described in U.S.
Patent 4,108,814 already incorporated herein,
bis(.beta.-hydroxyethyl)phosphinic acid (sodium salt, potassium
salt, triethylammonium salt), and the like: illustrative of the
compounds containing a potential cationic (ionic) group are
methyldiethanolamine (hydrochloride salt, acetic acid salt),
N,N-di(2-hydroxypropyl)aniline (hydrochloride salt, acetic acid
salt), N-cyclohexyl-N-(3-aminopropyl)propanol-2-amine
(hydrochloride salt, acetic acid salt), ethyldiethanolamine
(hydrochloride salt, acetic acid salt),
glycerol-.alpha.-bromohydrin quaternated with tributylamine
(ammonium salt), or triethyl phosphine (phosphonium salt),
glycerol-.alpha.-bromohydrin ternated with dimethyl sulfide
(sulfonium salt), and the like.
Preferred for the component (iii) is a class of dihydroxy alkanoic
acids described in U.S. Pat. No. 3,412,054 already incorporated
herein. When they are neutralized with any of the inorganic or
organic bases discussed in the incorporated references and also
above, they result in the preferred anionic moieties. Accordingly,
the preferred component (iii) is a carboxylic acid containing diol
which can be neutralized with an inorganic or organic base to form
said ionic group before, during or after said prepolymer formation.
The most preferred dihydroxy alkanoic acids are the
.alpha.,.alpha.-dimethylol alkanoic acids having the formula
QC(CH.sub.2 OH).sub.2 COOH wherein Q is hydrogen or C.sub.1 to
C.sub.8 alkyl (preferred are those acids with C.sub.1 to C.sub.4).
Preferred as the neutralizing agents are the aliphatic C.sub.2 to
C.sub.4 tertiary amines inclusive of triethylamine, tripropylamine,
tributylamine, triisopropylamine, and the like, and aqueous or
anhydrous ammonia. A most preferred embodiment of the present
invention is when the carboxylic acid group is neutralized with the
amine after said prepolymer formation and prior to forming an
aqueous dispersion thereof.
The proportions in which component (iii) is to be employed is not
particularly critical except to the extent that it be sufficient to
result in good dispersion of the prepolymer and final
polyurethane-urea in water. Advantageously, the component is
employed within a range of proportions such that the
milliequivalents of ionic groups per 100 grams of prepolymer (A)
falls within a range of from about 10 to about 150, preferably
about 20 to 100, most preferably about 25 to 75. The equivalent
weight of the ionic component is the precursor molecular weight
divided by the number of ionic groups. Accordingly, the proportion
of (iii) employed divided by its equivalent weight and multiplied
by 1,000 provides the ultimate milliequivalents of potential and/or
ionic groups present in the total prepolymer weight.
The isocyanate terminated prepolymer (A) as noted above is readily
prepared using the conventional procedures already incorporated
herein. The excess diisocyanate (i) along with the polyol mixture
(ii) and the difunctional isocyanate-reactive component (iii) are
brought together in any convenient manner, preferably under the
exclusion of moisture prior to the actual formation of aqueous
dispersion. This is best achieved by reacting the components under
an inert gas such as nitrogen or argon. In a preferred embodiment,
the isocyanate reactive components of (ii) and (iii) are first
thoroughly blended together followed by the excess
diisocyanate.
The exact proportion of excess of isocyanate is chosen so that the
final polymer properties desired will be obtained. Advantageously,
the proportions of (i), (ii) which includes both diol and triol,
and (iii) are such that the ratio of isocyanate equivalents to
total isocyanate-reactive equivalents in said prepolymer (A) falls
in a range of from about 1.1 to about 3, preferably from about 1.2
to 2.
The reaction temperature during prepolymer formation is normally
maintained below about 150.degree. C. Generally speaking, the
reactants will be heated to a temperature within the range of about
30.degree. C. to about 125.degree. C, preferably about 50.degree.
C. to 125.degree. C. In some cases, reaction exotherm will provide
heat thereby contributing to these temperature ranges. The presence
of a standard polyurethane catalyst in the prepolymer formation may
be desirable. The catalyst will speed up the prepolymer formation
and may allow better control of the process.
Solvents may be used during the prepolymer formation but one of the
benefits of the present invention is eliminating their use. If, for
whatever reason, a solvent is to be employed, then any of those
recommended in the incorporated references can be employed.
In respect of the neutralization, quaternarization or ternarization
step, whatever the case may be, it is preferred to carry it out
after the prepolymer has been formed, and, most preferably, before
the aqueous dispersion is prepared. The reason for the latter
preference is the more facile formation of the dispersion once the
ionic groups are present in the prepolymer. It is the
hydrophilicity of the ionic groups which give rise to the good
aqueous dispersibility of the prepolymer. Therefore, the
neutralizing acid, base, alkylating agent, or whatever as required
to convert the potential ionic group to its ionic form is added to
the rapidly stirred prepolymer in sufficient amount to react with
at least about 40 percent, preferably at least about 90 percent of
the potential ionic moieties
The aqueous dispersions are now easily formed simply by mixing the
prepolymer with the water, preferably under conditions of rapid
stirring or agitation. The concentration of prepolymer in the
aqueous dispersion is governed primarily by whatever is expedient
in the handling of increased volumes. However, the prepolymer is
advantageously present in a concentration of from about 10 percent
to about 50 percent by weight based on prepolymer and water.
Preferably, its concentration is from about 25 to about 40 percent.
These proportions should not be regarded as critically limiting for
depending on prepolymer properties and the types of ionic groups
involved, concentrations falling outside these ranges can be
observed.
It will be understood by those skilled in the art that aqueous
dispersions of isocyanate terminated prepolymers are not stable for
long periods. Accordingly, the lapse of time between preparation of
the prepolymer dispersion and the final polymer forming step should
be kept to a minimum. Notably, the prepolymer dispersions in
accordance with the present invention enjoy good stability both in
regard to their dispersion properties (no separation or settling of
solids or liquids) and their lack of reactivity between the
isocyanate groups and the water. Stability of the present
dispersions may be observed for periods of up to about two hours.
However, to ensure full isocyanate concentration, the polymer
curing step is preferably initiated within about 15 minutes of
formation of the prepolymer dispersion.
Completion of the polyurethane-urea formation, otherwise known as
chain extension is readily accomplished either by mixing the
prepolymer dispersion with the chain extender neat or in the form
of a solution in an organic solvent or water or by contacting the
prepolymer dispersion with a catalyst which facilitates the chain
extension of the prepolymer by water. Efficient intermixing of the
components is highly desirable when dealing with organic
dispersions in water. Accordingly, the mixing should be conducted
at high stirring speeds using efficient paddles or stirring blades.
If the extender is reasonably water soluble, it is preferable that
it be so employed as an aqueous solution. Any sequence of addition
using aqueous solutions or additional pure water to adjust final
dispersion concentration is possible during the prepolymer
extension step. In this regard, the weight percent of dispersed
polymer can be in any amount deemed appropriate for any particular
situation or ultimate application Conveniently, it can be present
in the same percentage proportions set forth above for the
dispersed prepolymer.
This chain extension will, for the most part, occur at ambient room
temperatures, i.e. 25.degree. C. to 30.degree. C. In some cases, an
exotherm may call for actual cooling. Although, the presence of the
aqueous dispersant acts as a heat-sink to modify reaction
exotherms. The reaction is generally conducted within a temperature
range of from about 5.degree. C. to 90.degree. C., preferably from
about 20.degree. C. to 60.degree. C. Mixing is continued until the
reaction is judged to be complete. The completion is easily
determined using conventional analytical procedures for measuring
the disappearance of the extender and/or isocyanate groups such as
by infrared measurements, gas phase chromatography, gel permeation
chromatography, and the like.
The preferred extenders (B) are defined above as the class of
hydrocarbon polyamines. The amine groups can be primary or
secondary or a mixture of both in the same molecule. Preferably,
the amine functionality falls within a range of from about 2 to
about 4, including average values within this range arising from
mixtures of polyamines. Preferred as a class are the hydrocarbon
diamines wherein the amine functions are primary.
Illustrative but non-limiting of the polyamines are
ethylenediamine, 1,3-propylenediamine, 1,4-butylenediamine,
1,5-pentylenediamine, 1,6-hexylenediamine, 1,7-heptylenediamine,
1,8-octylenediamine, 1,9-nonylenediamine, 1,10-decylenediamine,
2,2,4-trimethylhexamethylenediamine-1,6,
2,4,4-trimethylhexamethylenediamine-1,6, diethylene triamine,
triethylene tetramine, iminobispropylamine, and the like:
1,2-cyclohexylenediamine, 1,3-cyclohexylenediamine,
1,4-cyclohexylenediamine, 4,4'-isopropylidenebis(cyclohexyl amine),
4,4'-diaminodicyclohexyl, methylenebis(cyclohexylamine) including
the 4,4'-isomer, the 2,4'-isomer and mixtures thereof including all
their geometric isomers,
1-amino-3aminomethyl-3,5,5-trimethylcyclohexane, and the like;
1,3-phenylenediamine, 1,4-phenylenediamine, 2,4-toluenediamine,
2,6-toluenediamine, 4,4'-methylenebis(phenyl amine),
2,4'-methylenebis(phenyl amine), 4,4'-diaminobenzidine,
3,3'-diaminobenzidine, polymethylene polyphenylene amines, and the
like. Hydrazines may also be used.
More preferred as a class of extenders are those falling within the
alkylene diamines, most particularly the alkylene diamines of
C.sub.2 to C.sub.8 as exemplified above.
The proportion of amine extender (B) employed is governed by the
isocyanate content of the prepolymer component. Generally speaking,
the proportions of (B) are such that the ratio of isocyanate
equivalents in (A) to amine equivalents in (B) falls in a range of
from about 1.25 to about 0.90, and, preferably from about 1.10 to
0.95.
In the embodiment wherein the water is the chain extender, the
catalyst used to facilitate the chain extension can be any catalyst
known in the art for polyurethane formation. Examples of preferred
catalyst include organometallic catalysts, especially organotin
catalysts, and tertiary amine compounds. The preferred organotin
catalysts include, for example, stannous octoate,
dimethyltindilaurate, dibutyltindilaurate and the like. Suitable
tertiary amine catalysts include triethylenediamine. About 0.001 to
about 0.5 part of the organometallic catalyst is advantageously
used per 100 parts of reactive components. Tertiary amine catalysts
are suitably employed in an amount from about 0.01 to about 2 parts
per 100 parts of reactive components.
The resulting aqueous dispersions of ionic polyurethane-ureas in
accordance with the present invention can vary from milky to nearly
clear in their visual appearance. The dispersions or emulsions are
sometimes referred to as latexes. They are characterized by
excellent stabilities allowing them to be stored for long periods
which vary depending on such factors as ionic content
(hydrophilicity), storage temperatures, molecular weights in the
soft segments, and the like. Generally speaking, the dispersions
can be stored for days and transported within this period without
showing any signs of separating or gelling.
The physical properties of the final polymers obtained whether in
the form of films, coatings, or even stoving lacquers can vary from
those of soft elastomers to harder thermoplastics and all the way
to hard thermoset types depending on the polymer components and
proportions. Using amine extenders of functionality greater than 2
in combination with prepolymers having the highest isocyanate
contents results in the harder thermosets due to the high hard
segment content of the polymer and cross-linking. This is
particularly true when the soft segments in the prepolymer are
derived from the lowest molecular weight polyols. The terms "soft
and hard segments" refer to the polymer linkages derived from the
diisocyanate component with the high molecular weight polyols (ii)
and with the extender (iii) respectively. Reversing all of the
above conditions leads to the softer materials.
The polymer dispersions can be modified further by the addition of
colorants, latent curing agents, antioxidants, UV stabilizers,
fillers, fire-retardants, antistatic agents and the like.
Various kinds of substrates can be coated with films from these
aqueous dispersions. After the aqueous dispersions are brushed,
sprayed, poured, applied by dip-coating, dip-coagulation,
doctor-knife, or otherwise applied to a substrate such as woven and
non-woven textiles, leather, paper, wood, metals, ceramics, fibers,
plastics such as polycarbonates, acrylics, polyamides,
polyurethanes, polyesters, polystyrenes,
acrylonitrile/butadiene/styrene copolymers, polyethylenes, (high,
low and ultralow densities), rubbers including natural and
synthetic, and the like, the water is removed by conventional
drying methods.
Drying can be carried out either at ambient room temperatures
(e.g., 20.degree. C.) or at elevated temperatures, for example,
from about 25.degree. C. to about 150.degree. C., optionally under
forced-draft or vacuum. This includes the drying of static
substrates in ovens such as forced-air and vacuum ovens: or
continuously conveying the coated substrates through chambers
heated by forced air, high intensity lamps, and the like or under
reduced pressures.
In the preparation of free standing films, the techniques
particular to this art are readily applied. For example, the
aqueous dispersion can be poured into the appropriate mold, or
applied by doctor-knife to a metal or glass plate. Thereafter, the
water can be removed in stages using a series of different
temperatures with optional use of vacuum. Generally speaking, it is
preferred to initially remove the major amount (up to 25 percent)
of the water under forced air conditions and at low temperatures
(e.g., 20.degree. C. to 30.degree. C.). If the film has enough
structural integrity at this stage, it can be hung or optionally
oriented by placing under tension in the appropriate frame while
the remaining water is removed, preferably at an elevated
temperature, for example, from about 50.degree. C. to about
150.degree. C. Final conditioning of the film can be completed
under controlled conditions of heat and humidity.
The films in accordance with the present invention whether
deposited on a substrate or made as free standing films can be
prepared in any desired thickness. Typically, the films can have a
thickness of from about one mil to about 50 mils.
The excellent properties of the films include good clarity, high
gloss, good weather resistance including water repellency, abrasion
resistance, and the like. This makes them particularly useful in
the manufacture of waterproof clothing, tarpaulins, chip-resistant
coatings in automotive applications such as protective coatings
applied after a car has been painted, as coatings for high grade
paper, and the like. The present films provide excellent protective
coatings on aircraft acrylic canopies and in ballistic glazing
applications.
The figures illustrate several embodiments of the invention
described herein. In FIG. 1, one embodiment is shown where a
separate batch reactor is used for prepolymer formation, and a
second batch reactor is used to form polyurethane-urea ionomer. To
a prepolymer reactor (10) is fed a polyether diol, a polyether
triol, a difunctional isocyanate reactive component containing an
ionic group, and a diisocyanate. The polyether diol is transferred
from a diol holding tank (11) via transfer line (12). The flow of
the diol to the prepolymer reactor is controlled by valve (13). The
triol is transferred from a triol holding tank (14) via a transfer
line (15), with the flow controlled by a valve (16). The
diisocyanate reactive compound with an ionic group is transferred
from the holding tank (17) via a transfer line (18), where the flow
is controlled by a valve (19). The diisocyanate is transferred from
diisocyanate holding tank (20) via a transfer line (21), where the
flow is controlled by valve 22. The various reactants flow via the
transfer lines described (12), (15), (18) and (21) to a prepolymer
reactor feed line (23), which introduces the reactants to the
prepolymer reactor (10). The prepolymer reactor (10) has an
agitator (24) to insure mixing. In those situations where the use
of catalyst is desirable to speed up the prepolymerization, the
catalyst is transferred from the catalyst holding tank (25) via a
transfer line (26). The flow of catalyst is controlled by a valve
(27). The prepolymer reactor is jacketed with a heat exchange means
(28) the heat exchange means, is connected via a heat exchange
fluid feed line (29) and a heat exchange fluid return line (30) to
a source of steam (31) and cooling water (32). Once the reactants
have been charged to the prepolymer reactor (10), and mixing has
been started, the temperature of the prepolymer reactor (10) is
adjusted by the heat exchange means (28), usually the temperature
is raised. The prepolymerization reaction is allowed to take place
until substantially complete. A valve (35) is opened to allow the
neutralizing agent to be transferred from the neutralizing agent
holding tank (33) via transfer line (34) to the feed line (23) and
thus the feeding of the neutralization agent to the prepolymer
reactor. During neutralization it is often desirable for the
prepolymer reactor (11) to be cooled by passing cooling water
through the heat exchange means (28) surrounding the reactor. Once
the prepolymer is neutralized the prepolymer is transferred via
transfer line (36) to a second reactor (37), where such flow is
controlled by a valve (38). The second reactor (37) is adapted for
dispersion of the prepolymer. The second reactor (37) has an
agitator (39) for mixing the contents. After the prepolymer has
been charged, water is added via line (40) from water holding tank
(41). The flow of water is controlled by a valve (42). Water is
added to the second reactor (37) until a prepolymer in water
dispersion with the desired particle size is formed. Thereafter,
valve (43) is opened to allow the transfer of chain extender from
the chain extender holding tank (44) via a transfer line (45) to
the second reactor (37). The prepolymer dispersion and chain
extender are contacted in the second reactor (37) with mixing for a
period of time sufficient for the chain extension to go to
completion. Once the chain extension is complete, the product is
removed from the second reactor via transfer line (49). Once the
prepolymer has left the prepolymer reactor, and while the
prepolymer which has been transferred to the second reactor (37) is
being dispersed in water and chain extended. Another batch of
prepolymer is being formed in the prepolymer reactor (10) as
described before.
FIG. 2 illustrates an embodiment wherein three batch prepolymer
reactors sequentially feed prepolymer to a continuous reactor where
the water dispersion and chain extension takes place. In the figure
prepolymer is formed in a sequential manner in reactors (51), (52)
and (53) respectively. The prepolymer is transferred via transfer
lines (54), (55) and (56) respectively in a sequential manner to a
feed line (57) such that the feed line (57) can continuously feed
to the continuous reactor (58). The flow of prepolymer to the feed
line (57) is controlled via valves (59), (60) and (61)
respectively. The prepolymer is introduced into the second reactor
(58) through which it flows continuously. In a first zone (62) of
the second reactor water is added with mixing to form an emulsion.
The water is transferred from a water holding tank or source (63)
via a transfer line (64), where the flow to the second reactor (58)
is controlled by a valve (65). The prepolymer dispersion flows
through the second reactor to a second zone (66) wherein the chain
extender is added to the flowing prepolymer with mixing. The chain
extender is transferred from a chain extender holding tank (67) via
a transfer line (68) where the flow of chain extender is controlled
by a valve (69). The product is removed via line (70) from the
second reactor. The prepolymer reactors may be set up as described
in FIG. 1.
FIG. 3 demonstrates the embodiment wherein there is one prepolymer
reactor, a prepolymer holding tank adapted for holding prepolymer
before it is introduced to the second reactor, and a second reactor
for water dispersion and chain extension which is continuous.
Referring to FIG. 3, a first reactor (71) adapted for formation of
a prepolymer, is shown with a feed line 72 through which the
reactants are introduced. The reactor has a heat exchange means
(73) around it which is connected via a heat exchange introduction
line (74) and heat exchange fluid return line (75) to a source of
steam (76) and a source of cooled water (77). The prepolymer
reactor (71) contains an agitator (78). The prepolymer reactor (71)
is connected to a transfer line (79) adapted for transferring
formed prepolymer to a prepolymer holding tank (80). The flow of
prepolymer to the holding tank is controlled by a valve (81). The
prepolymer holding tank (80) is adapted for holding the prepolymer
before introduction of the prepolymer into the continuous reactor
(82) while more prepolymer is formed in the prepolymer reactor
(71). The prepolymer is transferred via line (83) to the continuous
reactor (82). The flow of prepolymer is controlled by valve (84) in
a manner such that a continuous flow of prepolymer is fed to the
continuous reactor (82). In the first zone (85) of the continuous
reactor the water is added to the flowing prepolymer to form an
aqueous dispersion. The water is transferred from a water holding
tank or source (86) via a transfer line (87) where the flow is
controlled via a valve (88). The prepolymer dispersion is flowed to
a second zone (89) where the chain extender is added to the flowing
aqueous dispersion. The chain extender is transferred from a chain
extender holding tank (90) via a transfer line (91) where the flow
is controlled by a valve (92). The product is removed from the
second reactor (82) via line (93).
FIG. 4 illustrates the embodiment in which two prepolymer batch
reactors sequentially feed one reactor designed for prepolymer
dispersion and chain extension. In FIG. 4 there are illustrated two
prepolymer reactors (101, 101') each have a feed line (102, 102')
for introduction of reactants to the prepolymer reactors (101,
101'). Each reactor is equipped with an agitator (103, 103') and a
heat exchange means (104, 104'), which is connected to a steam
source (105, 105') and cooling water source (106, 106') via a heat
exchange fluid introduction line (107, 107') and a heat exchange
fluid return line (108, 108'). After formation of the prepolymer as
described in the discussion of FIG. 1, the prepolymer is
sequentially transferred via transfer lines (109, 109') from the
reactors (101, 101'). The transfer lines (109, 109') are connected
to a valve (110) which controls the flow of the prepolymer from the
prepolymer reactors (101, 101') to a feed line (111) which
introduces prepolymer to a third batch reactor (112) adapted for
water dispersion and chain extension of the prepolymer. After a
batch of prepolymer is charged to the third reactor, agitation is
started or continued using an agitator (113). The water is
transferred from a water holding tank or source (114) via a line
(115) where the flow is controlled by a valve (116). The water is
added to form an aqueous dispersion of the prepolymer. Thereafter,
a chain extender is added by transferring it from a chain extender
holding tank (117) via a line (118) which is controlled by a valve
(119). The product is removed via a line (120). The timing of the
charges to the prepolymer reactors is such that a flow of
prepolymer to the third reactor is available as the reactions in
such reactors are completed. The prepolymer formation is the rate
limiting step.
* * * * *